Animal feeder

ABSTRACT

An animal feeder includes a cover for a container and a detector for the presence or absence of an animal. A first cam has an operating surface which is an extension of an outer surface of the cover. A second cam has an operating surface which is movable according to the detected animal presence or absence. The first and second cam surfaces are engaged whereby movement of the second cam surface in first and second opposite directions respectively causes the cover to open and close the container according to the detected presence or absence of the animal.

FIELD OF INVENTION

This invention relates to an animal feeder.

BACKGROUND ART

When supplying an animal with food, it is often desirable for the foodto be made accessible to the animal at any time over an extended period.Depending on the environment, this can lead to problems. These problemsmay include the tendency of the food to dry out, or to become stale, orthat it becomes contaminated by flies, dust or splashes. For thesereasons, it is desirable to provide the food with a cover, which caneasily be removed when the animal wishes to obtain access to the food.

Cats, for example, often prefer to leave food for future consumption,and they may be very particular about the condition of the food whenthey decide to eat.

An animal feeder will be described below, by way of example inillustration of the invention, which is economic, simple to operate, andeasily cleaned. Furthermore, although it is particularly suitable fordomestic animals, which are typically sensitive, it is also suitable forlivestock, and attractive for use in some wildlife applications.

SUMMARY OF THE INVENTION

In a particular animal feeder to be described below, by way of examplein illustration of the present invention, a container for an animal'sfood or liquid has a protective cover, which is normally closed, butwhich is operated to enable the animal to have access to the food orliquid when the animal pushes on a pedal. The feeder cover closesautomatically when the pressure is removed from the pedal. Thepedal-operated cover swings upwards to open in the particular feeder tobe described.

It is desirable that the animal's action should not cause the mechanismto move in a jerky, noisy, or unexpected way, so that it discouragesfurther use of the feeder. This is particularly important if the feederis to be used by hard-to-train animals such as cats. Thus, it isdesirable that the cover of the container should not start to open toorapidly. Even more important, perhaps, is that at the end of themovement of the opening of the cover no excessive noise is created, andthat the base of the feeder is not caused to move significantly.Similarly, the closure of the cover must be reasonably smooth,draught-free, and quiet.

BRIEF DESCRIPTION OF THE DRAWING

The following description and drawings disclose, by means of examples,the invention which is defined in the appended claims, whose termsdetermine the extent of the protection conferred hereby.

In the drawings:—

FIG. 1 is a diagrammatic side view of an animal feeder,

FIG. 2 is a diagrammatic plan view of the feeder shown in FIG. 1,

FIG. 3 is a diagrammatic end view of the feeder shown in FIGS. 1 and 2,

FIG. 4 shows at (i) and (ii) diagrammatic side views of an alternativecounter-balanced cover for a feeder,

FIG. 5 is a series (i) to (iv) of diagrammatic partial sectional viewsfor use in describing a way of assembling a cover to the base of afeeder,

FIG. 6 shows at (i) to (iv) a series of diagrammatic partial side viewsfor use in illustrating a cam operating feature of a cover for a feeder,and

FIG. 7 shows at (i) and (ii) diagrammatic partial side views of anextended pedal operating arrangement for a cover.

DETAILED DESCRIPTION OF THE DRAWING

Referring to the drawings, and particularly to FIGS. 1 and 2, there areshown a food container 1 forming a base and having a cover 2. The cover2 is pivoted for rotation with respect to the container 1 about an axisor fulcrum 3 defined by a rod 4 which is carried by the container orbase 1. An extension 5 from the cover 2 passes beneath and is curvedaround the rod 4 in order to locate the cover 2 for rotation about therod 4, as best seen in FIG. 5.

A pedal 6, which has a wide central portion 7 and side arms 8 is shownwith short studs 9 extending inwardly from the arms 8 for location inslots or grooves 10 in respective sides of the container base 1 wherebythe pedal is able to pivot about the studs 9 resting at the bottom ofthe slots or grooves 10 in the container base 1. The food container 1has a central depressed region in which food, water, or other liquid canbe placed.

The ends of the side arms 8, which are remote from the wide centralportion 7 of the pedal 6, have cam portions 11 with smoothly curved camsurfaces 12 at their edges which cooperate at 24 with curved camsurfaces 13, of cam portions 14 depending from the cover 2. The camsurfaces 13 have a part 15 which is oppositely curved from the remainderand which, as will be described below provides a braking action.

As best seen in FIG. 3, the cover 2 extends at its sides 16 over the camportion 14, that serve to retain the studs 9 in the slots 10, althoughit is not necessary to have these side portions 16.

Referring to FIG. 4, there are shown at 4(i) and 4(ii), side views of analternative form of cover 2 a that includes an extension for acounterweight 17 thereby modifying the position of the centre of gravityof the cover such that the closing moment reduces as the coverapproaches closure. At 18 there is shown the fulcrum of the cover 2 a,about which it pivots with respect of the base 1, and at 19 the centreof gravity of the cover 2 a is indicated. The counterweight 17 may bepermanent, or interchangeable to enable different mechanical effects tobe provided, or it may be omitted.

Referring now to FIG. 5, there are illustrated diagrammatically in 5(I)to 5(iv) successive steps in the assembly and operation of the cover 2on the base 1.

In FIG. 5( i) the cover 2 is shown being lowered, as indicated by anarrow 20, until the curved extension 5 rests upon the rod 4, as see inFIG. 5( ii). The cover 2 is then rotated about the rod, as indicated byan arrow 21 in FIG. 5( iii) until it rests upon the top of the containeror base 1. The views are diagrammatic and do not show the cam portion14.

Referring now to FIG. 6, the cover 2 is shown in 6(i) resting around itsrim on the rim of the base 1. The curved cam portion 11 on the side arm8 of the pedal 6 is shown resting on the curved cam surface 13 of thecam portion 14.

A construction line 23 shown on the drawing extends at right angles tothe point of contact 24 between the cam surface 13 and the cam surface12 and provides a datum line for measuring the distances from the line23 to the fulcrum 3 of the cover 2, and the pivot point 9 of the arm 8,which are indicated by y and x respectively.

The relative movement of the line 23 and of the contact point 24, duringan opening movement of the cover 2 resulting from the action of thepedal 6, will now be described reference to FIGS. 6( i) to 6(iv).

The drive from the pedal 6 to the cover 2 can provide a gradual startand end to the motion of the cover 2. In the arrangement begindescribed, the motion of the cover 2 to open the container 1 iscontrolled by a rolling and sliding contact between the cam surface 12of the cam 11 on the pedal lever 6 and the cam surface 13 on the camportion 14 forming a part of the cover 2. The construction of theserolling and sliding surface 12 and 13 is such that the amount ofslippage is small, minimizing the amount of work required to overcomefriction. To derive the relative rates of motion of the pedal 6 and thecover 2, reference is made to the construction line 23 normal to the(moving) contact point 24 between these two cam surfaces. The relativerate of angular movement (cover: pedal) is equal to the ratio of the(shortest) distances (x:y) between the line 23 and the pedal 6 stud 9(that forms a fulcrum) and the cover 2 fulcrum 3 respectively. Theamount of slippage between the cam surfaces 12 and 13 can be kept low byensuring that the cam contact point 24 remains reasonably close to theline joining the stud 9 and the cover fulcrum 3. The shape of the camsurfaces 12, 13 thus allows fine control to be provided of the movementof the cover 2, including the ability to stop the motion of the cover 2by reversing the direction of the controlling moment on the cover 2. Inthe particular arrangement being described this capability may beunderstood from the following description.

With the cover 2 closed (FIG. 6( i)), the line 23 is relatively far fromthe fulcrum 3, the cover 2, (i.e. ‘y’ is large) and so a relatively highmechanical advantage is maintained. Then, as the cover 2 starts to open,the initiating force required to move the pedal 6 downwards is low andthe speed of opening is minimised. Once started (FIG. 6( ii)) the valueof ‘y’ reduces; and the value of ‘x’ is reasonably constant, themechanical advantage is thus reduced, and the cover 2 is openedrelatively rapidly. Shortly before the motion of the cover is requiredto stop (FIG. 6( iii)), the mechanical advantage reduces further. Theextent of this reduction is at such a level that the accelerating forceon the cover 2 is rather small, and the resistance to motion of thepedal 6 becomes significant. Finally (FIG. 6( iv)), the line 23 passesvery close to the fulcrum 3 for the cover 2 and the opening momentbecomes near to zero (so that any further movement of the pedal dependsprimarily on its resilience), and the oppositely curved part 15 at theend of the cam surface 13 provides a stop to the movement of the cover2. The reduction in the opening forces applied to the cover 2 to thebraking effect of the part 15 of the cam surface 13 minimises noise andjarring forces on the base 1 of the feeder. In the arrangement shown,releasing the pedal 6 allows the cover 2 to close under its own weight.Alternative methods to drive and restore the cover 2 can include the useof springs, and of linkages coupled to the pedal 6, for example.

Referring to FIG. 7, there is shown an extension platform 26 which ishinged or otherwise loosely connected at 27 to the pedal 6 to provide aramp which rests at its end 28 on the ground, or on an extension fromthe base 1. The connection 27 may be provided by pins on the pedal 6which slide in a slot in side portions of the platform 26, so that, asan animal climbs the ramp provided by the platform 26, the platform 26pivots about its point of rest at its end 28 on the ground or on theextension from the base 1, and slides on the ground. The extension 26 isconstructed from a number of sections optionally hinged together, in onealternative arrangement.

In another arrangement the ramp section or extension platform 26 is usedto assist in training the animal and subsequently removed. For trainingpurposes the platform 26 may initailly be comparatively long, and itslength may be reduced according to the progress of the training. Thusthe ramp, or extension platform 26 may be made of a series ofinterlocked sections.

Furthermore, provision may be made to hold the cover 2 open beyond aparticular location during the training procedure, for example by meansof a peg and holes in relatively moving parts, such as the pedal 6 andthe container base 1.

Advantageously, to minimise the number of holes, the level of restraintmay be made to depend on the orientation of the peg. While the hole andthe inserted part of the peg may be round, there is advantage in theirbeing formed to fit in specific orientations only. This would reduce therisk that the pegs would unintentionally rotate during use. Marking ofthe orientations and positions would make it simple to make thereduction of the height of the opening progressive. Particularlysuitable shapes for the sections of such orientation keys includeregular polygons, because their shapes can ease both moulding andcleaning. When the cover is constrained from closing, the methodsdescribed above to avoid disturbance during closing will not be fullyfunctional. Accordingly, it may be advantageous to provide means toadjust the balance of the cover, so that the cover does notautomatically close itself during the critical part of the trainingperiod.

During the training period, it may well be beneficial to restrict accessto the feeder to the side from which the pedal extends, for example byplacing the feeder within a box or bay having three sides.

It will be appreciated that the particular arrangement described is madefrom three parts, which may be taken apart easily for cleaning.

The use of a cover 2 with low inertia, for example a transparentlightweight plastics material, has various benefits. For example, itallows the contents of the container to be seen and it assists inslowing the rate at which the cover closes.

The control of the movement of the cover 2 may also effected by thecounterbalancing effect of the cam portions 14. In the arrangement ofFIG. 4, the centre of gravity 19 of the cover 2 is below its fulcrum 18when the cover 2 is closed. This result may be achieved either by thedimensioning of the parts of the cover 2, or by employing thecounterbalance weight 17. By these means both the opening and theclosing forces applied to the cover 2 may be carefully controlled.

It will be appreciated that other forms of linkage between the pedal andthe cover, including the use of springs and levers may be employed.However, the comparatively simple drive via cam surfaces is preferred,due to its simplicity and ease of cleaning, and the fact that it gives arolling and sliding action with a minimum of slipping giving a gradualstart and finish to the movement of the cover 2.

The amount of slippage between the cam surfaces 12 and 13 can beminimised by ensuring that the cam contact point remains reasonablyclose to the line joining the fulcrum of the pedal and the fulcrum ofthe cover.

The container base 1, may have sections for specific foods or liquids,or it may be designed to employ separate containers for the food andliquid, which are removable.

Provision may be made beneath the food container section of the base 1for means to regulate the temperature of the container, for example iceblocks.

Other means than a pivoted pedal which is operated physically by ananimal may be employed to actuate the cover 2. For example, the cover 2may be opened and closed using an electrically powered mechanism. Such amechanism may be caused to open or close the cover 2 according to thedetection or absence of an animal. Various forms of sensor, includingheat detecting, pressure sensitive and capacitive, or using optical,sound, or infrared technology may be used to detect the presence orabsence of an animal and to control the operation of the electricallypowered mechanism.

It will be appreciated that although in the particular arrangementdescribed there is provided a braking surface part 15 on the cam surface13 which is directed oppositely to the remainder of the surface 13, itis possible to provide a braking surface part on the cam surface 12which follows a different curve from that of the remainder of thesurface 12.

A sensor which is specific to a characteristic of a particular animal,or to a characteristic of a device carried by a particular animal, maybe used to ensure that the feeder cover is opened or closed according tothe presence or absence of the particular animal only.

There has thus been described, by way of illustration, in onearrangement, an animal feeder that has a base, a cover pivoted to thebase with a cam at one end, and a lever, or a system of levers, thatcouples or couple the cover to a pedal, one of the levers incorporatinga cam that is in contact with the cover, whereby, when the pedal isdepressed, the cover opens.

It is preferred that the interface between the cam on the cover and thecam that contacts it should be a rolling and sliding contact, whereinthe contact between the cams is maintained sufficiently close to a linejoining the fulcrums controlling the two cams that the sliding part ofthe motion minimises the wear and the frictional loss resulting from thecontact. A pedal lever pivoted to the base may be used to drive thecover without the aid of intermediate levers. In one arrangement, thelever that drives the cover directly is pivoted at one end to the baseand at the other to a further lever that acts as a platform or pedallever, the other end of the platform or pedal lever being either free toslide on the surface that supports the base of the feeder, or beingprevented from sliding relative to the base.

In the particular illustrative arrangements described the cover swingsupwards around a fulcrum that is provided near to the end of the feederremote from the pedal. It is preferred that the rolling-sliding contactbetween the cover and the cam that drives it should be such that themotion of the cover begins gradually. Furthermore, the driving moment onthe cover preferably becomes low as the cover approaches its fully openposition. The rolling sliding contact between the cam on the lever andthe cover limits the opening of the cover in a preferred arrangement byreversing the direction of the controlling moment on the cover. Bymaking the inertial mass of the cover sufficiently small it is possiblethat it experiences an air damping effect which is significant inslowing its motion. The provision of resilience and or absorbency in thepedal, in the lever and or in the cover helps to minimise jarring whenthe cover is held in its fully open position. The balance of the coverin the illustrative arrangements described causes it to close whenpressure is removed from the pedal.

Another feature of the particular illustrative arrangement that has beendescribed is that the line joining the fulcrum of the cover to itscentre of gravity should become nearly vertical as the cover closes. Theeffect of the air damping of the cover mentioned above may be enhancedby means of a lip around the edge of the cover, or the edge of the basewith which the cover cooperates, so that the effect of air damping ismaximised when the feeder is nearly closed. Resilience may be providedto the base or to the cover in the region where the base and cover makecontact only when the feeder is substantially closed.

It will be appreciated that the base of the feeder may be used directlyas a container for food and/or drink, and/or that space may be providedin the base of the feeder for supplementary containers for food and/ordrink.

Such a container may provide separate sections for different foods,and/or for food and for drink. Furthermore, space may be provided in thebase of the feeder in which ice, cold-blocks or some other coolingmechanism may be provided for the food/drink. Such space may ideally beimmediately underneath a food/drink container.

The feeder which has been described by way of example may readily beassembled and disassembled for ease of cleaning, and the key parts ofthe feeder may be made from dishwasher-proof material.

In one arrangement, means is provided to prevent the cover from closingin order to assist in training the animal or animals in the use of thefeeder, and more than one setting for a minimum opening of the cover ispossible, determined for example by the insertion of a peg or pegs intothe base of the feeder. The adjustment of the size of the opening of thecover may be achieved by placing a peg into one of a selection of holesin the base of the feeder. The adjustment of the size of the opening isachieved in one arrangement by virtue of the orientation of a peg in thehole or holes.

In such an arrangement the hole or holes and the peg are so made thatthe peg will not rotate while it remains inserted in the hole(s). Thecross-section of a hole and of the inserted section of the peg areregular polygons in one arrangement. Marking may be provided in order toease the identification of the extent of the minimum opening.

It is possible, in one arrangement to modify temporarily the balance ofthe cover so that it does not automatically close when the pressure onthe pedal is removed.

The pedal arrangement may include a ramp hinged or jointed to the usualpedal, this ramp being so arranged that the animal will climb the rampmore easily as the animal approaches the bowl of the feeder, therebyopening the cover of the feeder.

A pedal arrangement is able to operate without the ramp. The ramp may beused to assist in training and put to one side thereafter. The length ofsuch a ramp may be adjusted according to needs, and the length of theramp may be progessively reduced by the removal of a section orsections, during training. The ramp in one arrangement is made fromsections, at least some of which may be easily assembled anddisassembled.

The removal of the sections may be effected by breaking them from theramp, or from sections of the ramp, and the sections may be of unequallength, and be used in different combinations. It is possible for morethan one section to be suitable as the immediate driver for the pedal.

Means may be provided that allow the animal to approach the feeder fromone or more desired directions only. The direction of approach may beconstrained by screens attached to the feeder and the screens may beremoved when not required.

In one arrangement the direction of approach is constrained by placingthe feeder in a bay. Such a bay may be constructed from the packaging inwhich the feeder was transported or displayed, and the packaging may beso designed that its use as a bay does not significantly impair itssubsequent reuse as packaging for the feeder. It will be appreciatedthat the cover for the food is preferably made from transparentmaterial, so that the food can be seen by the animal and that the basehas a non-slip lower surface or non-slip and resilient feet.

In the particular arrangements described by way of example inillustration of the invention, the cam surfaces 12 and 13 are both shownas being curved. However, it is not essential for the surfaces 12 and 13to be of the shape shown. They may have some other shape giving thenecessary cooperative action which results in the cover 2 being openedand closed, as required. One or both of the cam surfaces may, forexample, be plane. In one arrangement, instead of a cam surfaceassociated with a pedal 6 being simply rotated in operation about a stud9 (that forms a fixed pivot point) as a result of pressure on the pedal6, the pedal may have a sliding movement with respect to the base 1, andcause an associated cam surface which may be partly plane to slide alonga linear path over at least a part of its movement.

It will be understood that, although particular arrangementsillustrative of the invention have been described by way of example,variations and modifications thereof, as well as other arrangements maybe made within the scope of the appended claims.

1. An animal feeder including a base for a container for food, a coverfor the container, the cover having an outer surface, a pedal arrangedfor operation in response to a force exerted against the pedal by a bodypart of an animal, a first cam having a first operating cam surfacewhich is an extension of an outer surface of the cover and a second camhaving second operating cam surface which is coupled with the pedal andmovable in response to the body part of the animal depressing the pedal,the first and second cam surfaces being in engagement, whereby movementof the second cam surface in a first direction in response to the bodypart of the animal depressing the pedal causes the cover to open thecontainer and movement of the second cam surface in a second directionopposite to the first direction in response to the body part of theanimal no longer depressing the pedal causes the cover to close thecontainer, and the first cam operating surface comprising a first curvedportion and a second curved portion, the first curved portion and thesecond curved portion having opposite curvatures, the first curvedportion adapted to contact the second cam surface during movement in thefirst and second directions, and the second curved portion defining abrake to resist movement of the second cam in the first direction.
 2. Ananimal feeder as claimed in claim 1, in which the first cam operatingsurface is pivoted for rotation with the cover.
 3. An animal feeder asclaimed in claim 1, in which the second cam is rotatable about a pointon the base.
 4. An animal feeder as claimed in claim 1, in which atleast a part of the movement of the second cam is around a circularpath.
 5. An animal feeder as claimed in claim 1, in which the cover isrotatable with respect to a fulcrum on the base and in which when thecover is closed, the point of engagement between the first and secondcams is relatively far from the fulcrum, and in the open position of thecover the point of engagement between the first and second cams isrelatively close to the fulcrum.
 6. An animal feeder as claimed in claim5, wherein the cover includes a counter balance to the movement of thecover.
 7. An animal feeder as claimed in claim 5, wherein at least apart of the cover is transparent, the transparent portion being arrangedfor enabling the animal to see the contents of the container while thecover closes the container, and wherein the cover has a center ofgravity below the fulcrum when the cover is closed and when the cover isopen.
 8. An animal feeder as claimed in claim 5, wherein the cover isdimensioned so as to have a center of gravity below the fulcrum when thecover is closed and when the cover is open.
 9. An animal feeder asclaimed in claim 5, wherein the cover includes a counterweight forcausing the cover to have a center of gravity below the fulcrum when thecover is closed and when the cover is open.
 10. An animal feeder asclaimed in claim 1, in which the pedal includes a hinged extension. 11.An animal feeder as claimed in claim 1, wherein the cover is made from alow inertia lightweight plastics material.
 12. An animal feeder claimedin claim 1, wherein at least a part of the cover is transparent, thetransparent portion being arranged for enabling the animal to see thecontents of the container while the cover closes the container.
 13. Ananimal feeder as claimed in claim 1, wherein the first operating camsurface of the first cam and the second operating surface of the secondcam are outside the container.
 14. An animal feeder as claimed in claim13, wherein the operating cam surface of the first cam and the secondoperating surface of the second cam are arranged to roll upon each otherto provide for smooth and regular movement of the cover throughout itsmovement between the open and closed conditions of the container.
 15. Ananimal feeder as claimed in claim 1, wherein the operating cam surfaceof the first and the second operating surface of the second cam arearranged to roll upon each other to provide for smooth and regularmovement of the cover throughout its movement between the open andclosed conditions of the container.
 16. An animal feeder as claimed inclaim 1, wherein the first curved portion comprises a first convexsurface, the second curved portion comprises a first concave surface,and the second cam operating surface comprises a second convex surface.17. An animal feeder as claimed in claim 16, wherein the first convexsurface has a first radius of curvature and the second convex surfacehas a second radius of curvature substantially equal to the first radiusof curvature.
 18. A cat feeder including a base for a container forfood, a cover for the container, the cover having an outer surface, apedal arranged for operation by a foot of a cat, a first cam having afirst operating cam surface which is an extension of an outer surface ofthe cover and a second cam having second operating cam surface which iscoupled with the pedal and movable in response to the foot of the catdepressing the pedal, the first and second cam surfaces being inengagement, whereby movement of the second cam surface in a firstdirection in response to the foot of the cat depressing the pedal causesthe cover to open the container and movement of the second cam surfacein a second direction opposite to the first direction in response to thecat no longer depressing the pedal causes the cover to close thecontainer, and the first cam operating surface comprising a firstconvexly curved portion and a first concavely curved portion, the firstconvexly curved portion corresponding to a first part of its surfacethat contacts the second cam operating surface during movement in thefirst and second directions, and the first concavely curved portioncorresponding to a second part of its surface defining a brake to resistmovement of the second cam in the first direction.
 19. The cat feeder asclaimed in claim 18, wherein at least a part of the cover istransparent, the transparent portion being arranged for enabling the catto see the contents of the container while the cover closes thecontainer.
 20. The cat feeder as claimed in claim 18, in which the firstcam operating surface is pivoted for rotation with the cover.
 21. Thecat feeder as claimed in claim 18, in which the second cam is rotatableabout a point on the base.
 22. The cat feeder as claimed in claim 18, inwhich at least a part of the movement of the second cam is along alinear path.
 23. The cat feeder as claimed in claim 18, in which thecover is rotatable with respect to a fulcrum on the base and in whichwhen the cover is closed, the point of engagement between the first andsecond cams is relatively far from the fulcrum, and in the open positionof the cover the point of engagement between the first and second camsis relatively close to the fulcrum.
 24. The cat feeder as claimed inclaim 23, wherein the cover includes a counter balance to the movementof the cover.
 25. A cat feeder as claimed in claim 23, wherein at leasta part of the cover is transparent, the transparent portion beingarranged for enabling the cat to see the contents of the container whilethe cover closes the container, and wherein the cover has a center ofgravity below the fulcrum when the cover is closed and when the cover isopen.
 26. A cat feeder as claimed in claim 23, wherein the cover isdimensioned so as to have a center of gravity below the fulcrum when thecover is closed and when the cover is open.
 27. A cat feeder as claimedin claim 23, wherein the cover includes a counterweight for causing thecover to have a center of gravity below the fulcrum when the cover isclosed and when the cover is open.
 28. The cat feeder as claimed inclaim 18, in which the pedal includes a hinged extension.
 29. The catfeeder as claimed in claim 18, wherein the cover is made from a lowinertia lightweight plastics material.
 30. The cat feeder as claimed inclaim 18, in which at least a part of the cover is transparent, thetransparent portion being arranged for enabling the cat to see thecontents of the container while the cover closes the container.
 31. Ananimal feeder as claimed in claim 18, wherein the operating cam surfaceof the first cam and the second operating surface of the second cam arearranged to roll upon each other to provide for smooth and regularmovement of the cover throughout its movement between the open andclosed conditions of the container.
 32. An animal feeder as claimed inclaim 18, wherein the second operating cam surface comprises a secondconvex surface.
 33. An animal feeder as claimed in claim 32, wherein thefirst convex surface has a first radius of curvature and the secondconvex surface has a second radius of curvature substantially equal tothe first radius of curvature.